That's why there was an international agreed to distress call, although
at the time, radio operators were NOT obligated to listen or act upon it.


I forgot to add that that is also not correct.

For British Ships at least, and I expect most other countries had similar
legislation, the Merchant Shipping Act, did and still does *require* a
vessel to render assistance to another vessel in distress; regardless of how
you find out about it.

You are confusing it with the fact there was no requirement to keep a
listening watch for distress traffic.

Regards
Jeff